Distillation process and system adopting solid alkali for coking wastewater

Abstract

The invention relates to a distillation process and system adopting a solid alkali for coking wastewater. The system comprises a distillation tower, a solid feeding device, a mixing tank, a raw material wastewater-ammonia distillation wastewater heat exchanger, an ammonia distillation wastewater cooler and an ammonia distillation wastewater pump; and the top of the mixing tank is provided with a gas-phase balance opening, the upper part of the mixing tank is provided with a mixed alkali liquor outlet, the lower part of the mixing tank is provided with a solid inlet, a raw material wastewater inlet and a produced liquid inlet, and a stirring device is arranged in the mixing tank. The solid alkali is added into the mixing tank through the solid feeding device, the solid alkali and the raw material wastewater are mixed to form an alkaline solution, the alkaline solution directly enters the upper portion of the distillation tower, or the solid alkali and a liquid phase extracted from the middle side line of the distillation tower are mixed to form an alkaline solution, and the alkaline solution returns to the middle of the distillation tower again to be used as an alkali source for decomposing fixed ammonium in the ammonia distillation process. The solid alkali is used for replacing a liquid alkali in the prior art, the liquid-phase load of the distillation tower can be reduced, sothat the use amount of heating steam and cooling circulating water can be reduced, the discharge amount of ammonia distillation wastewater can be reduced, and the purposes of energy conservation andenvironmental protection are achieved.

Description

technical field [0001] The invention relates to the technical field of coke oven gas purification, in particular to a coking wastewater distillation process and system using solid alkali. Background technique [0002] Coking wastewater mainly comes from residual ammonia water, crude benzene separation water and sewage from gas purification units. Coking wastewater contains volatile ammonia, fixed ammonium, H 2 Hundreds of inorganic / organic pollutants such as S, HCN and tar. The complex types of these pollutants and poor biodegradability have brought great difficulties to the harmless treatment of coking wastewater. With the increasingly stringent environmental protection requirements, the "Coking Chemical Industry Pollutant Discharge Standard" (GB 16171-2012) clearly stipulates the discharge limits for existing enterprises, new enterprises and areas that implement special protection measures for water pollutants. Coking wastewater treatment puts forward more stringent req...

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Problems solved by technology

[0010] The above patent documents all use liquid alkali as the way of supplementing alkali to decompose and fix ammonium. Although the technological purpose of decomposing and fixing ammonium is achieved, it also increases the liquid phase load of the ammonia distillation tower, thereby increasing the consumption of steam and cooling water at the bottom of the tower. Amount and discharge of ammonia distilled wastewater

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